In the field of endoscopy it is necessary to introduce a gas into a body cavity in order that endoscopic procedures can be accomplished. Customarily an insufflator is provided for this purpose. It injects gas into the cavity through a cannula that penetrates into the cavity through an incision. Usually other incisions are also made to accommodate operating instruments and viewing instruments.
The injection of a gas into the human body must be very carefully regulated. Conventional insufflators include considerable circuitry to govern and limit the rate of flow of the gas, and the maximum pressure permitted in the cavity. The risks of over-pressure and of over-supply are well-known. Another more frequently encountered problem is that a too-little flow to accomplish the insufflation is supplied.
Known insufflators are quite bulky and are placed to one side on a support. The gas is fed to the cavity through a connecting tube to a cannula or trocar. It is fundamental that every surface which contacts insufflating gas must be non-contaminating. If a reverse pressure occurs and body fluids back up into the insufflator, considerable work must be done to clean up existing devices.
There are other problems. The usual insufflation pressure in the cavity is on the order of 15 mm Hg, and gas flow rates between about 10-20 liters per minute are needed. When gas at those pressures and rates must be passed through measuring orifices as well as through a cannula, it is not physically possible to supply such volumes at such low pressures through a suitably small-bore hose. Accordingly it is common practice to supply gas to the cavity itself at much higher pressures, on the order of 50 mm Hg, and to use a larger-bore hose in so doing. It is an inherent disadvantage of such systems. To avoid the risk of over-pressurizing, the gas is supplied in a series of short bursts, and the cavity pressure is measured so as to stop or reduce the number of bursts when an appropriate pressure is reached. The bore of the hose must therefore be quite large.
Such an arrangement also requires an elaborate control mechanism, which must control both the rate of flow and its output pressure to the trocar, because all of the response to cavity pressure is from within the control mechanism, which is located relatively far from the trocar.
It is an object of this invention to provide a self-regulating insufflator which receives gas under substantial pressure through a small-bore hose, which continuously regulates the pressure being supplied, and which is continuously responsive to cavity pressure.
It is another object of this invention to enable the use of a gas supply control mechanism to this insufflator which controls only the gas flow rate. Regulation of the actual supply and maintenance of cavity pressure is made a function of the insufflator itself. A control which merely supplies gas to establish and maintain a predetermined pressure, working from a high pressure source that supplies the gas at a given flow rate is much simpler than an insufflator which must also respond to varying conditions in the cavity. The fact that the supply hose is not also used to monitor cavity pressure results in considerable simplification.
The supply of gas to establish a predetermined pressure and to supplement the supply to make up for leakage is only one part of the problem. Over-pressure in the cavity is another. During endoscopic procedures, gases are supplied or generated from other sources, such as argon-beam coagulators, smoke evacuators, and coolant devices for lasers, all of which raise the cavity pressure. Relief of such over-pressure is also essential.
Significant economies can result, and safer supplies that can be entirely pneumatic can be made with this invention. Electronics will not be necessary, and explosive gases can be supplied without the precautions that are required when electrically controlled units are used. This instant invention is believed to be the first high rate of flow insufflator device which is entirely pneumatic, and which is therefore useful for supplying explosive gases.
It is another object of this invention to provide an insufflator which can conveniently be held by the hand, which is self-regulating, which can be supplied through a very small hose. It can be made so inexpensively that it can economically be discarded if the surgeon does not wish to have it cleaned and sterilized. Alternatively, parts of it may be made disposable, such as the regulator and hose, while a metal cannula or trocar could be sterilized and re-used for years.
This invention provides such an insufflator. It can be constructed also to accommodate a viewing or operating instrument, or a separate trocar, thereby reducing the number of incisions which must be made.